1. Field of Invention
This application relates, in general, to an extraction cell assembly with quick-release seal removal, and more particularly to a cap assembly for use with Accelerated Solvent Extraction (ASE) cells that allows easy removal and replacement of a seal and/or bed support by a user without the use of tools.
2. Description of Related Art
Analyses of organic compounds are becoming increasingly important. It is also necessary to isolate and analyze trace levels of compounds from a variety of sample matrices such as soil, sediments, food, animal tissue, fruits and vegetables. Sample preparation constitutes an important step prior to analysis. Extraction is an integral part of sample preparation. Accelerated Solvent Extraction (ASE) is a technique used for extracting the analytes of interest using a solvent at elevated temperatures and pressures. The elevated pressure elevates the boiling point of the solvent thereby allowing faster extraction to be conducted at relatively high temperatures. Thus the extraction process is significantly faster than traditional methods such as Soxhlet extraction. A cell to hold the sample as well as a filter, for example, a frit, are integral components of an ASE instrument. The cell facilitates the extraction and in-line filtering.
ASE extractions occur at relatively high pressures (e.g., 1500 psi), and operating at such high pressures requires careful design of the extraction cell. An extraction cell generally includes a conduit or main cell body that has end caps sealing the cell body (see, e.g., sample cells, FIG. 1). The role of the end cap is to seal the cell body and to facilitate easy access into the cell. The end cap also includes a seal and a bed support or filter that retains the solid components within the cell. Facile replacement of these parts would add to ease of use from a user perspective.
With reference to FIG. 2, current cell assemblies generally include a cell body and a pair of cell end cap assemblies (only a bottom end cap is shown in FIG. 2). With continued reference to FIG. 2, each end cap assembly includes, from bottom to top, an end cap, a frit, a seal, an annular cap insert, and a snap ring to lock everything within the end cap.
An exemplar of an existing cell assembly is described U.S. Pat. No. 5,647,976 which shows a high pressure and temperature cell for solvent extraction.
Such current cell assemblies provide robust end caps that seal cell assemblies properly at elevated temperature and especially at elevated pressures (e.g., 1500 psi). The cell body is generally threaded inside the cap insert, but the liquid seal occurs between the edge of the cell body against a seal. This sealing mechanism allows the cell to be operated at high pressure without any solvent leaks.
The seal and the frit need periodical replacement after extractions and/or after they become dirty from exposure to the sample conditions. And for trace analysis, the user needs to replace the components after each analysis to minimize carry over.
A user needs to disassemble the entire end cap assembly to replace either the seal or the frit in the existing current cell assemblies. And to disassemble, a user must use an appropriate snap ring tool to remove the snap ring and thus release the cap insert, seal and frit from the end cap.
One will appreciate that the appropriate snap ring tool must be readily available, and that use of the snap ring tool requires a degree of skill and manual dexterity to remove and properly install the snap ring. Dislodging the seal and the bed support after prolonged use may further require the user to tap the end cap to release the seal and the bed support.
In light of the foregoing, it would be beneficial for an end cap design that facilitates easy removal and replacement of the end cap components.